Technical Field
The present invention relates to the field of wireless communications technologies, to a power control method for improving a switch spectrum characteristic of a radio frequency power amplifier, and also to a power control device for implementing the foregoing power control method and a communication terminal including the power control device.
Related Art
A radio frequency power amplifier (RF PA) is widely applied to communication terminals such as mobile phones. In a pre-stage circuit of a transmitter, power of a radio frequency signal generated by a modulation and oscillation circuit is very small, and an RF PA needs to perform a series of amplifications in a buffer stage, an intermediate amplification stage, and a final power amplification stage to obtain a sufficient radio frequency power, so as to feed the power to the antenna to radiate it. In this process, accurate power control is critical to ensuring normal use of a communication terminal.
At present, there are various mobile communications standards or wireless communications standards, such as GSM, TD-LTE, WCDMA, and Wi-Fi, in the market. Accurate power control within a large dynamic range is required in all of the communications standards. An output characteristic of the RF PA needs to comply with relevant communications standards. For example, output power control needs to satisfy a requirement of a burst mask. To satisfy the requirement, a power control circuit is usually provided with a specific circuit to detect a saturation degree, but an implementation method thereof is often too complex.
For example, in an existing power control circuit, the foregoing requirement is satisfied by setting a voltage of a base electrode of a bias power amplifier. A signal of the voltage is formed by lineally combining a power control signal and a reference voltage. Although in a case of a low power, this solution improves power-added efficiency, in a case of a high power, particularly in a case of a high power and a low supply voltage, a phenomenon of switch spectrum degradation is likely to occur in this solution.
The Chinese Patent Application with the Publication No. CN102354242A discloses a power control circuit, which may dynamically adjust a voltage of a base electrode of a power amplifier according to requirements of different output powers, so as to achieve an objective of current optimization. The power control circuit includes an error amplifier, a regulator, and a current detection circuit. The current detection circuit detects a current flowing through the power amplifier, and generates a detection signal. Such a signal may be a voltage or a current. In a specific implementation, the current flowing through the power amplifier may be copied and scaled down according to a proportion. Upon further modulation performed by an input power control signal, the copied current is fed back to the error amplifier. Hence, the error amplifier generates an output voltage to control the base electrode of the power amplifier, thereby achieving an objective of dynamically controlling the voltage of the base electrode so as to optimize the current. However, such a solution also has the following advantage: when a supply voltage of a mobile terminal is excessively low, a switch spectrum characteristic of the power amplifier may still be degraded.